Upregulation of stress response genes and ABC transporters in anaerobic stationary-phase Mycobacterium smegmatis

Oxygen starvation triggers an adaptive stationary-phase response in Mycobac terium smegmatis. During this anaerobic stationary phase, RNA synthesis con tinues at a low but significant level. Employing a modified expressed-seque nce-tag (EST) approach, in combination:with the M. tuberculosis genome data and comparative Northern analysis, we have identified the first genes that show an increase in transcription in M. smegmatis cells that have entered anaerobic stationary phase. One gene encodes the counterpart of the M. tube rculosis NifS-like protein Rv1464. Two genes are homologues of M. tuberculo sis Rv1460 and Rv3368c, of unknown: function. Strikingly, several genes ind uced by oxygen starvation encode putative stress protection proteins (count erparts of M. tuberculosis DnaK, Rv0350; betaine-aldehyde dehydrogenase, Rv 0768; thioredoxin reductase, Rv3913) and ABC transporters (counterparts of M. tuberculosis Rv1463, Rv1473, Rv3197). We conclude that development of ge neral stress resistance and certain active transport processes might play a role in the survival of oxygen-starved M. smegmatis.